Sheet type heating element and method of manufacturing the same

ABSTRACT

Water is adhered to the bottom face of a non-woven fabric having a large number of pores, then a heat generating powder composition is sprayed onto the top face of this fabric to be held in place. Another non-woven fabric is then superposed on the top face of the first non-woven fabric and the two non-woven fabrics are compressed. Water or a solution of electrolytes in water is then sprayed on the fabrics. Thereby, a sheet shaped heat generating body can be provided which uses a heat generating composition which generates heat when contacting air, which prevents concentration of the heat generating composition in one direction, and which is thin, flexible and has good heat generating properties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention broadly relates to sheet shaped heat generatingbodies, particularly to such thin and flexible heat generating sheetswhich reduce displacement and concentrate placement of heat generatingcomposition, and the manufacturing method thereof

2. Related Art

Heat generators which have as their main component oxidizable metalssuch as iron powder are widely used as pocket heaters, wherein the heatgenerating composition which contacts with oxygen in the air to emitheat is packed in air permeable bags.

Although these kinds of heat generators are advantageous in that theymay be used in a simple manner, they have problems in that when wearingthe generator on the body, the heat generating composition moves down tothe bottom of the bag due to its weight, not only during sports but alsowhen standing still, so that the change of shape causes an uncomfortablefeeling to the wearer and the heat generating feature becomes lesseffective.

Various efforts have been made to hold the heat generating compositionin or between supporting members to form a sheet-like product as a meansfor reducing these defects. Described below are examples of suchefforts:

a) A method of holding the heat generating composition with wire mesh ornet shaped plastic objects (Patent Laid-Open Sho 53 (1978)-84246Publication);

b) A method of superposing metal foils such as aluminum foils onnon-woven fabric made of activated carbon fiber and impregnated withchloride, water or other oxidation auxiliary agents (Patent Laid-OpenSho 63 (1988)-37181 Publication);

c) A method of spraying a heat generating agent on Japanese paperimpregnated with an oxidation auxiliary agent, and thereafter subjectingit to pressure to mold such product into a sheet-like shape (UtilityModel Sho 64 (1989)-42018 Publication);

d) A method of laying one over the other a plurality of non-wovenfabrics made of heat-fused fibers which may include plant fibers, andthen distributing chemical heat generating agent therein (PatentLaid-Open Hei 2 (1990)-142561 Publication); and

e) A method of distributing heat generating agent on a supporting sheetwhich comprises unevenly layered fibers with a large number of very finepores, and to hold the agent thereon (Patent Laid-Open Hei 3(1991)-152894 Publication).

Technical Problems to be Solved by the Invention

However, the related art described above has the following problems inthe manufacturing process of the heat generating sheet or the resultingheat generator.

a) When holding the generator with wire mesh or net shaped plasticobjects, the sheet-like product becomes more rigid and is impracticalfor use, and the heat generating composition powder becomes easilydetached.

b) In products made by superposing metal foils such as aluminum foils onnon-woven fabric made of activated carbon fibers, etc. impregnated withoxidation auxiliary agents, the metal surface area is considerably smallin comparison to products using metal powders, such that a good heatgenerating effect cannot be achieved. If the number of foils isincreased, this results in reducing the flexibility of the product.

c) In products made by spraying the heat generating agent on paper whichis then subjected to pressure to form a sheet, the heat generating agentcomes off through folding or shaking, which is not practical.

d) The combination of a plurality of non-woven fabrics by utilizing thewater holding property of plant fibers and the heat fusion of syntheticfibers not only renders the structure and processing complicated, butalso has practical problems in that the sheet-like object lacksflexibility due to instances where the non-woven fabrics do not adhereto each other, depending on the type and blending ratio of the heatfusive fibers and due to the rigid net-like structure in heat fusion.

e) Concerning the method of distributing heat generating compositions onthe supporting sheet made of irregularly layered fibers with a largenumber of very fine pores, this is a good method in that the compositionmay be distributed and held inside the pores in a homogenous manner.However, due to the fact that after securing the iron powder, asuspension liquid containing activated carbon, etc. is sprayed, it isdifficult to hold the heat generating composition as a whole in ahomogenous mixture.

As shown above, it is strongly desired to develop a flexible heatgenerating body, wherein the heat generating sheet is manufactured so asto allow easy and homogenous distribution and holding of the heatgenerating composition while preventing leakage of the powder, and amethod of manufacturing the same.

SUMMARY OF THE INVENTION

The inventors of the present invention have conducted research aimed atsolving the problems described above with the goal of obtaining a thin,soft heat generating sheet with high heat generating capacity, whereinthe heat generating composition is securely held without beingdisplaced. The present invention achieves this goal by dampening thebottom face of a multi-poric, non-woven fabric with water and thereafterspraying a heat generating powder composition from the top face of saidnon-woven fabric and holding such powder.

In other words, the present invention is a heat generating sheetcharacterized in that after adhering water to the bottom face of a firstnon-woven fabric, a heat generating powder composition is sprayed on thetop face of such fabric and held inside its pores. A second non-wovenfabric is then superposed on the top face of the first non-woven fabricand compressed via a mold compressor to form a sheet product. The sheetproduct is then impregnated with water or a solution of electrolytes inwater. Alternatively, the present invention is a heat generating sheetcharacterized in that water is adhered to the bottom face of amulti-poric, first non-woven fabric and/or the top face of a secondnon-woven fabric. The second non-woven fabric is then superposed on thebottom face of the first non-woven fabric. A heat generating powdercomposition is then sprayed onto the top face of the first non-wovenfabric and held inside its pores. A third non-woven fabric is thensuperposed on the top face of the first non-woven fabric and iscompressed via a mold compressor to form a sheet product. The sheetproduct is then impregnated with water or a solution of inorganicelectrolytes in water. In a third embodiment of the present invention, aheat generating sheet is characterized in that a plurality of layers ofnon-woven fabric in a combination of non-woven fabrics are superposedvia water adhesion or water adhesion plus compression, and at least oneof said non-woven fabric layers holds a heat generating composition. Thepresent invention also relates to a method of manufacturing each of theembodiments.

The present invention holds the heat generating composition with a firstnon-woven fabric by moistening the bottom face of the first non-wovenfabric and spraying the heat generating powder composition from the topface, thereby causing homogeneous holding of the powder in the firstnon-woven fabric without leakage. Then, by superposing a secondnon-woven fabric thereon and compressing them, the non-woven fabrics donot separate, securing the fixing of the sheet shape, and providing aheat generating composition which is thin and flexible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of heat generating sheet 1.

FIG. 2 is a cross sectional view of heat generating sheet 1'.

FIG. 3 discloses the first example for performing the steps of thepresent invention.

FIG. 4 discloses the second example for performing the steps of thepresent invention.

FIG. 5 discloses the third example for performing the steps of thepresent invention.

FIG. 6 is a diagram showing the heat generative properties of thepresent invention.

FIG. 7 is a cross sectional view of a plaster-type, sheet-shaped pocketheater.

EMBODIMENTS OF THE INVENTION

The present invention may be applied to heat generators for warming thehuman body, warming animals and plants, heating and warming foods, andalso heating and warming machines and equipment, etc., and themanufacturing method of such generators.

The non-woven fabric used in the present invention is a multi-poric,non-woven fabric, which has the property of being able to hold such heatgenerating composition material described below which is a materialmixture used in powder form (hereinafter referred to as "powdercomposition") inside its pores, having great moisture holding capacity,and is mainly composed of plant fibers such as pulp, cotton and linen,or recycled fibers such as rayon. In addition, a mixture of plant fibersor recycled fibers with a slight amount of synthetic fibers such asnylon, polyester, acryl or polyolefin may be used, too. Among thesematerials, preferable is a non-woven fabric wherein the total sum ofplant fibers and recycled fibers is 95% or more of the fiber content,because of their large moisture holding capacity and their ability tomaintain the flexibility of the sheet without causing heat fusion whenheating the product to compress and mold a sheet-shaped product. Morepreferably, the product utilizes a non-woven fabric which contains 98%or more of pulp, cotton, linen or rayon, etc.

There are no particular limits to the method of manufacturing the firstnon-woven fabric, which may be formed by an entanglement of fibermaterials, or formed by using a small amount of adhesive agent orsynthetic resin, etc. as binder. The greater the porosity rate of thefirst non-woven fabric, the easier the distribution of the powdercomposition into the pores, but as pores which are too large incurleakage of the powder, the porosity rate is normally 70-99.5%,preferably 80-99%.

The thickness of the first non-woven fabric is normally 0.5-25 mmdepending upon the amount of heat generating composition to be held, andthe porosity rate of the first non-woven fabric is preferably 1-10 mm.The measuring weight is normally 5-200 g/m², preferably 30-150 g/m².

In the present invention, the spraying of the composition material onthe top face of the first non-woven fabric is conducted such that wateris adhered to the bottom face of the first non-woven fabric, and thenthe composition material to sprayed thereon. By causing water to adhereto the bottom face of the first non-woven fabric, even large-pored,non-woven fabrics can hold powder without leakage due to the adhesion ofwater.

The amount of water to adhere to the bottom face of the first non-wovenfabric need only be such so as to prevent leakage of powder compositionfrom the bottom face of the first non-woven fabric by the moisture,which is normally 10-200 g/m² depending upon the measuring weight,thickness and material quality, etc. of the first non-woven fabric, andpreferably 20-120 g/m².

The water adhesion method need only be such so as to enable adjustmentof the amount of the adhering water and a homogenous adhesion, forexample the method of atomizing or sticking water with a roll on thebottom face of the first non-woven fabric.

In the present invention, the material composing the powder compositionis, for example, oxidizable metal powder, activated carbon,water-holding agent.

Concerning the inorganic electrolytes, they are one component of thepowder composition if mixed as solid body into the materials above, andif sprayed and impregnated in the form of aqueous solution after themolding of the sheet, for example, they are not included into the powdercomposition.

The oxidizable metal powder is iron powder and aluminum powder, etc.,but normally, iron powder is used, namely reduced iron powder, atomizediron powder, electrolytic powder, etc.

Activated carbon is used as the reactive agent and also as the waterholding agent, and is normally palm activated carbon, wood flour carbon,or peat carbon, etc.

The inorganic electrolytes used are preferably chlorides of alkalimetals, alkali earth metals and heavy metals, and sulfates of alkalimetals, for example sodium chloride, potassium chloride, calciumchloride, magnesium chloride, ferric chloride, sodium sulfate, etc.

The water holding agent is pearlite powder, vermiculite, macromoleculicwater holding agent, etc., but is preferably a macromoleculic waterholding agent.

The particle size of the powder composition is normally not more than 60mesh, preferably containing at least 50% of particles which are notlarger than 100 mesh.

The heat generating composition is made by adding and mixing water or asolution of inorganic electrolytes in water to the powder compositiondescribed above. The blending ratio in the whole of the heat generatingcomposition cannot be specified in general, as it depends upon theproperties and shape of the non-woven fabric, and the heat generatingfunction to be achieved. As an example, when setting the oxidizablemetal powder as 100 parts by weight, the activated carbon may be 5-20parts by weight, the inorganic electrolytes 1.5-10 parts by weight, andwater 25-60 parts by weight.

In addition, it is also possible to mix water holding agents such aspearlite powder, vermiculite or macromoleculic water holding agent, orhydrogen generation depressor or consolidation preventor, as desired.

Among those described above, the water, or the water and inorganicelectrolytes will be supplied after the molding into a sheet shape.

Examples of the method of holding the heat generating composition insidethe pores of the first non-woven fabric are as follows: a) spraying themixture of powder material such as iron powder, activated carbon,inorganic electrolytes and the like on the first non-woven fabric, thensubjecting the fabric to vibration to cause the mixture to proceedinside the pores to be held therein; or b) spraying the mixture ofpowder materials with exception of the inorganic electrolytes such asiron metals and activated carbon onto the top of the first non-wovenfabric, subjecting the fabric to vibration to cause the mixture toproceed inside the pores to be held therein, then, after the molding toa sheet shape, spraying such inorganic electrolytes as a solution insalt water. In both cases a) and b), the alternative to subjecting thefabric to vibration is to subject the first non-woven fabric to suctionfrom the bottom direction, thereby causing distribution and holding ofthe powder.

Among these two, method b) is preferable in that the inorganicelectrolytes can be distributed on the whole surface in a homogenousmanner.

As stated above, by causing water to stick to the bottom face of thefirst non-woven fabric and spraying and holding the powder composition,the composition material itself is secured by the adhesion of water tothe wet bottom face of the first non-woven fabric, so that thedistribution of powder composition tends to increase from the bottomface of the first non-woven fabric to its top face.

The amount of heat generating composition to be held inside the firstnon-woven fabric depends upon the thickness of the first non-wovenfabric, the final thickness of the heat generator and the desired heatgenerating effects, etc., but is normally 150-10,000 g/m² of supportivebody, and preferably 1,000-5,000 g/m².

If the held amount is less than 150 g, the generated heat temperatureand duration of the generated heat are reduced, but when the held amountexceeds 10,000 g, the heat generator becomes thicker, so that themolding of a thin and flexible sheet becomes difficult.

The second non-woven fabric functions to hold the powder compositionremaining on the top face of the first non-woven fabric and to preventleakage of the powder composition from the top face, so that preferably,it has a large water holding capacity and has no heat-fusion property,so that it is a non-woven fabric made of the same material as that ofthe first non-woven fabric, namely pulp, cotton, linen or rayon, etc.

It is desirable for the porosity rate of the second non-woven fabric tobe slightly smaller than that of the first non-woven fabric, normally60-99%, and preferably 70-98%. Otherwise, if the porosity rate is toolarge, the powder is likely to leak.

The thickness of second non-woven fabric depends upon its porosity rateand the amount of powder composition held. Its thickness is normally0.1-10 mm, preferably 0.5-5 mm. Its weight is normally 5-150 g/m², andpreferably 20-100 g/m².

In the present invention, the layered product containing the firstnon-woven fabric which holds the powder composition and the secondnon-woven fabric is compressed by a compressor and processed into theshape of a sheet. The compression may be conducted by utilizing apressing machine or pressing roll on the layered product. Thecompression may be conducted by using a plane or flat roll, but in orderto prevent separation of the compressed sheet in the non-woven fabrics,it is preferable to form protrusions in the shape of waves, turtlebacks,rings, polka dots, stitch designs or others to form an embossed face.

The compressing may be conducted under heating. Heat compressing isadvantageous in that the moisture heating secures the fixing of theshape even more.

The compression temperature and pressure depend upon the materialqualities of the first and second non-woven fabrics and the amount ofpowder composition to be held, which cannot be specified in general. Asan example, when using a heating roll with embossed face, thetemperature normally ranges from ordinary temperature up to 300° C., andthe linear pressure from around 0.5 through 300 kg/cm. In this way, theshape of the load is secured in the compressed state, forming a thinsheet.

The thickness of the heat generating sheet will be selected according tothe heat generation to be achieved and the use, but in order to utilizethe properties as a sheet to design them as thin as possible, they arenormally 6 mm or less, preferably 4 mm or less. Concerning the size, thesheet will be cut in appropriate sizes according to the purpose of use.

Water is supplied to the sheet product through atomization or rolladhesion. This includes the amount of the water or the solution ofinorganic electrolytes in water with which the sheet product is eitherto be impregnated as one component of the heat generator, or the totalamount of water and inorganic electrolytes.

The sheet-like heat generator described above is stored in this state,or, in order to obtain those heat generating properties corresponding toits use, in a bag made of laminated film of polyethylene havingpermeable pores and non-woven fabric, or a bag made of a permeable filmwith micropores, then sealed in a non-permeable bag for storage, to beused as pocket heaters or medical heat generating bags.

In addition, the bag may also be used for warming animals and plants,heating and warming foods, and heating and warming machines andequipment, etc.

In the present invention, when holding the powder composition in thefirst non-woven fabric, it is possible to superpose a fine, thirdnon-woven fabric on the bottom face of the first non-woven fabric toprevent powder from falling out of the first non-woven fabric even whenits pores are large.

The third non-woven fabric may be composed mainly of materials such asof pulp, cotton, linen, rayon and other fibers, namely non-woven fabricmade of pulp, cotton, linen, or rayon, etc. and paper-like products suchas tissue paper.

The weight of the third non-woven fabric is normally 5-150 g/m², andpreferably 10-100 m².

When superposing the third non-woven fabric on the bottom face of thefirst non-woven fabric, water maybe applied to the bottom face of thefirst non-woven fabric and/or the top face of the third non-woven fabricand then superposed. By thus superposing the first and third non-wovenfabrics in a moist state, they are superposed in a close manner throughtheir moisture adhesion, requiring no adhesive agent, which is a greatadvantage.

The amount of water to be applied to the non-woven fabric is normally10-200 g/m², preferably 20-150 g/m².

In the present invention, when superposing the second non-woven fabricon the top face of the first non-woven fabric, water may first beadhered to the bottom face of the second non-woven fabric, andthereafter be superposed. The method of adhering water to the secondnon-woven fabric may be water atomizing or roll adhesion, and theapplied amount is normally 15-300 g/m², preferably 30-200 g/m².

Instead of adhering water to the bottom face of the second non-wovenfabric, it may be adhered to the top f ace of the first non-wovenfabric, or on both non-woven fabrics. When adhering water to the topface of the first non-woven fabric, a portion of the powder compositionmay scatter when using certain adhesion methods, so that the method ofadhesion to the second non-woven fabric is preferable.

When superposing first and second non-woven fabrics with the applianceof water, the fabrics are superposed closely onto each other due towetness adhesion, which not only prevents the heat generating powdercomposition material from scattering, but also allows smoothintroduction into the compressor, and when using a heating compressor,the moist heating effect allows a secure fixing of the shape, which aregreat advantages.

According to the present invention, the sheet made of first and secondnon-woven fabrics, and the sheet made of first, second, and thirdnon-woven fabrics are sheet products superposed through water adhesionand compression adhesion.

By superposing a plurality of these heat generating sheets, a productmay be made by superposing a plurality of layers of heat generatingsheets. During the manufacture process of the sheet product, it is alsopossible to stack the non-woven fabrics asthird-first-second-first-second from the bottom, or asthird-first-first-first-second from the bottom, and cause the powdercomposition to be mainly held within the first non-woven fabric.

By superposing a plurality of layers as described above, the thicknessof the heat generator may be determined arbitrarily. The plurality oflayers are superposed by water adhesion, or water adhesion pluscompression adhesion, while at least one of such layers is a heatgenerator holding heat generating powder composition, which avoids astrong three-dimensional wired structure, so that it is an effectiveflexible heat generator.

PREFERRED EMBODIMENTS

Now, the present invention will be exemplified with reference to thedrawings, and explained more specifically. It is understood that thespecific embodiments are for illustrative purpose and the presentinvention is not limited such embodiments.

FIG. 1 is a cross sectional view of a heat generating sheet 1 accordingto the present invention.

FIG. 2 is a cross sectional view of a heat generating sheet 1' carriedout in a different mode from that of FIG. 1. In both FIGS. 1 and 2,reference numeral 2 indicates a first non-woven fabric, referencenumeral 3 indicates a second non-woven fabric. Reference numeral 4indicates a heat generating composition held in first non-woven fabric2. Reference numeral 5 indicates the heat generating composition held innon-woven fabric 3. Reference numeral 6 indicates a third non-wovenfabric.

FIG. 3 discloses a first example for performing the steps of the presentinvention. In FIG. 3, a roll 7 of first non-woven fabric 2 is providedfor use with the present invention. Water is applied to first non-wovenfabric 2 on its bottom face by a water atomizer 9. First non-wovenfabric 2 is then subjected to roll 10, sprayed with the powdercomposition at powder filler 11, and then subjected to vibration to holdthe heat generating composition inside the pores of first non-wovenfabric 2.

Then, second non-woven fabric 3, supplied by a roll 8, is superposed viaa roller 13, heat compressed at a compressor 14, cut into the desiredsize by a cutter 15, and then sprayed with a solution of inorganicelectrolytes in water at salt water sprayer 16 to finally form heatgenerating sheet 1.

FIGS. 4 and 5 illustrate second and third examples for performing thesteps of the present invention when superposing non-woven fabric 6 on abottom face of first non-woven fabric 2.

The heat generating sheet obtained as above is packed in bags withadjusted permeability in accordance with their use, and used as pocketheaters or medical equipment by successively utilizing the method ofsealing such sheet in non-permeable bags.

FIG. 7 is a cross sectional view of a plaster-type pocket heater using aheat generator sheet according to the present invention. Referencenumeral 19 indicates an inner bag, reference numeral 20 a layer ofadhesive agent, reference numeral 21 separating paper, and referencenumeral 22 an outer bag.

Embodiment 1

In the device shown in FIG. 3, first non-woven fabric 2, approximately1.9 mm thick, weighing approximately 57 g/m² and with an approximateporosity rate of 97.9%, made of wooden pulp (Habix K. K.; "J Soft") wassent with 12.3 m/min speed. Water was homogeneously atomized on a bottomface of first non-woven fabric 2 at a rate of 35 g/m². Then, a mixtureof 90% iron powder, 8% activated carbon, 2% macromoleculic water holdingagent was sprayed from a top face of first non-woven fabric 2 at a rateof 1,100 g/m², and at the same time, first non-woven fabric 2 was shakenup and down to hold such mixture in its pores. Thereafter, secondnon-woven fabric 3, made of wooden pulp with thickness of 1.1 mm,weighing 40 g/m², and a porosity rate of 97.6% (Honshu Selshi K. K.,"Kinokurosu") was superposed on the top face of first non-woven fabric2, and the sheet was put through a heat compressing roller to form theshape of a sheet. The heat compressing roller was embossed face withstriped design on the roller face, and set at 195° C., with linearpressure of 40 kg/cm.

Then, the sheet product was cut in the size of 8.5 cm×12.5 cm.Thereafter, a salt water solution which is a mixture of 8.5% sodiumchloride and 91.5% water was sprayed at the rate of 520 g/m² to obtainan approximately 2 mm thick heat generating sheet. This heat generatoris flexible and the heat generating composition is held in place. Thisheat generator was stored in a flat shaped inner bag, of which one faceis composed of a multi-layered sheet with a microporic film made ofpolypropylene with 350 g/m² day moisture permeability and a nylonnon-woven fabric, and of which the other face is composed of a laminatedfilm of polyethylene film and nylon non-woven fabric to form the heatgenerating sheet. This was further sealed in a non-permeable bag, thenstored.

After two days, the heat generating sheet was taken out of the outer bagand indoor measurements were conducted concerning the heat-generatingeffect based on the JIS S-4100 heat generation test method at roomtemperature 20° C. and relative humidity 65%. As a result, the heatgenerating effect shown in FIG. 6 was obtained.

The temperature exceeded 40° C. after 8.5 minutes, and reached 52° C. in70 minutes. The duration of heat generation for 40° C. or more wasapproximately 10 hours.

Furthermore, when taking this heat generating sheet out of the outer bagand wearing it on the body, a comfortable temperature could be obtainedfor around 12 hours, while always maintaining a flexible sheet shape.

Embodiment 2

In the device shown in FIG. 4, first non-woven fabric 2 made of woodenpulp (Habix K. K.; "J Soft"), approximately 1.9 mm thick, weighingapproximately 57 g/m² and with an approximate porosity rate of 97.9%,was sent with 12.3 m/min speed, and water was homogeneously atomized onthe bottom face of first non-woven fabric 2 at a rate of 40 g/m². Then,after superposing a tissue paper of 30 g/m² measuring weight on thebottom face of first non-woven fabric 2, a mixture of 90% iron powder,8% activated carbon, 2% macromoleculic water holding agent was sprayedfrom the top face of first non-woven fabric 2 at a rate of 1,100 g/m²,and at the same time, the non-woven fabric was shaken up and down tohold such mixture in its pores. Thereafter, an the top face of firstnon-woven fabric 2, second non-woven fabric 3 made of wooden pulp, 1.1mm thick, weighing 40 g/m², and with a porosity rate of 97.6% (HonshuSeishi K. K.; "Kinokurosu") was superposed after having water adhered toits bottom face at the rate of 60 g/m².

Thereafter, the heat generating sheet was obtained in the same way as inEmbodiment 1.

This heat generator is flexible and there was no falling of the heatgenerating composition. This heat generating sheet was stored in a flatinner bag, of which one face is a multi-layered sheet of microporicpropylene film with a moisture permeability of 350 g/m² day and a nylonnon-woven fabric, and of which the other face is a laminated film ofpolyethylene and nylon non-woven fabric to form a sheet-shaped heatgenerating bag. This bag was further sealed in a non-permeable outerbag.

After two days, the heat generating sheet was taken out from the outerbag and measurements made with regard to its heat generating effect inthe same way as in Embodiment 1. As a result, the temperature exceeded40° C. after 9 minutes, and reached 52° C. in 65 minutes. The durationof heat generation of 40° C. or more was approximately 11 hours.

Furthermore, when this heat generating sheet was taken out of the outerbag and worn on the body, a comfortable temperature could be obtainedfor around 12 hours, while always maintaining a flexible sheet shape.

Embodiment 3

Using the device shown in FIG. 5, the water atomization on the bottomface of first non-woven fabric 2 ("J Soft") was replaced with thefollowing: 30 g/m² water was atomized on the top face of a tissue paperwith measuring weight 30 g/m² to moisten the paper, which was thensuperposed on the bottom face of first non-woven fabric 2 ("J Soft") toobtain the heat generating sheet in the same way as in Embodiment 2.

This heat generator was flexible and allowed no falling of the heatgenerating composition.

Embodiment 4

Using the device shown in FIG. 4, first non-woven fabric 2 made ofwooden pulp, approximately 1.2 mm thick and weighing 40 g/m² (HonshuSeishi K. K.; "Kinokurosu") was sent with 12.3 m/min speed, and waterwas homogeneously atomized on the bottom face of first non-woven fabric2 at a rate of 40 g/m². Then, after superposing a tissue paper of 27g/m² measuring weight on the bottom face of first non-woven fabric 2, amixture of 90% iron powder, 8% activated carbon, 2% macromoleculic waterholding agent was sprayed from the top face of first non-woven fabric 2at a rate of 1,430 g/m², and at the same time, first non-woven fabric 2was shaken up and down to hold such mixture in its pores. Thereafter, onthe top face of first non-woven fabric 2, second non-woven fabric 3 madeof wooden pulp, 1.5 mm thick and weighing 60 g/m² (Honshu Seishi K. K.,"Kinokurosu") was superposed after having water adhered to its bottomface at the rate of 60 g/m². This sheet was put through a heatcompressing roller with an embossed face with striped design on theroller face and set at 200° C., linear pressure 166 kg/cm to form theshape of a sheet.

In order to measure the flexibility of this sheet, a test piece 25 mmwide and 88 mm long was cut therefrom, and, using the Galle method setforth in JIS L-1096 and a bending repulsion test unit, the bendingrepulsion of this sheet was measured.

Also, salt water which is a mixture of 8.5% sodium chloride and 91.5%water was sprayed on the sheet at the rate of 608 g/m², then a testpiece was immediately cut therefrom and the bending repulsion measured.As a result, the bending repulsion before spraying of the salt water was1217 mgf, and that after the spraying of the salt water was 1450 mgf

Thereafter, the heat generating sheet was obtained in the same way as inEmbodiment 1 with the exception that the salt water to be sprayed was608 g/m².

This heat generator is flexible and there was no falling out of the heatgenerating composition. This heat generating sheet was stored in a flatinner bag, of which one face was composed of a multi-layered sheet ofmicroporic film made of polypropylene with a moisture permeability of350 g/m² day and a nylon non-woven fabric, and of which the other facewas composed of a laminated film of polyethylene and nylon non-wovenfabric with an additional layer of adhesive agent and separation papersuperposed thereon to form a sheet-shaped heat generating bag. This bagwas further sealed in a non-permeable outer bag.

After two days, the heat generating sheet was taken out from the outerbag and measurements made with regard to its heat generative effect inthe same way as in Embodiment 1. As a result, the temperature exceeded40° C. after 8 minutes, and reached 52° C. in 65 minutes. The durationof heat generation for 40° C. or more was approximately 12 hours.

Furthermore, when this heat generating sheet was taken out of the outerbag and worn on the body, a comfortable temperature could be obtainedfor around 12 hours, while always maintaining a flexible sheet shape.

Comparative Example 1

In the device shown in FIG. 4, first non-woven fabric 2, approximately2.5 mm thick, weighing 38 g/m², with a 98.7% porosity rate, made of 50%polyester and 50% heat fusion polyester (Marusan Sangyo K. K."Estermelty") was sent with 12.3 m/min speed, and water washomogeneously atomized on the bottom face of first non-woven fabric 2 ata rate of 40 g/m². Then, after superposing tissue paper weighing 27 g/m²on the bottom face of first non-woven fabric 2, a mixture of 90% ironpowder, 8% activated carbon, and 2% macromoleculic water holding agentwas sprayed from the top-face of the non-woven fabric at a rate of 1,430g/m². At the same time, first non-woven fabric 2 was shaken up and downto hold such mixture in its pores. Thereafter, on the top face of firstnon-woven fabric 2, second non-woven fabric 3, made of wooden pulp 1.5mm thick and weighing (Honshu Seishi K. K.; "Kinokurosu") was superposedafter having water adhered thereto at its bottom face at the rate of 60g/m². This sheet was put through a heat compressing roller with anembossed face with striped design an the roller face, and set at 200° C.and linear pressure 166 kg/cm to form the shape of a sheet.

The same flexibility test as with Embodiment 4 was carried out for thissheet. As a result, the bending repulsion before spraying of the saltwater was 2647 mgf, and that after the spraying of the salt water was2267 mgf Thereafter, the heat generating sheet was obtained in the sameway as in Embodiment 4.

This heat generator did not show any falling out of the heat generatingcomposition, but was hard compared to the heat generating sheet ofEmbodiment 4 and flexibility was low.

This heat generating sheet was stored in a flat inner bag, of which oneface was composed of a multi-layered sheet of microporic propylene filmwith a moisture permeability of 350 g/m² day and a nylon non-wovenfabric, and of which the other face was composed of a laminated film ofpolyethylene and nylon non-woven fabric with an additional layer ofadhesive agent and separation paper superposed thereon to form asheet-shaped heat generating bag. This bag was further sealed in anon-permeable outer bag.

After two days, the heat generating sheet was taken out of the outer bagand continued to hold a comfortable temperature when worn on the bodyand maintained the sheet shape, but was always hard, causing anuncomfortable feeling.

What is claimed is:
 1. A sheet shaped heat generating body comprising asheet product impregnated with water or a solution of inorganicelectrolytes in water, said sheet product including:a porous, firstnon-woven fabric with water adhered to a bottom face of said firstnon-woven fabric; a heat generating powder composition sprayed on a topface of said first non-woven fabric to be held inside pores of saidfirst non-woven fabric; and a second non-woven fabric superposed on saidtop face of said first non-woven fabric, wherein said first non-wovenfabric and said second non-woven fabric are compressed via a moldcompressor to form the sheet product.
 2. A sheet shaped heat generatingbody comprising a sheet product impregnated with water or a solution ofinorganic electrolytes in water, wherein said sheet product comprises:afirst non-woven fabric; a third non-woven fabric superposed on a bottomface of said first non-woven fabric; a second non-woven fabricsuperposed on a top face of said first non-woven fabric; and a heatgenerating powder composition sprayed from the top face of said firstnon-woven fabric to be held inside pores of said first non-woven fabric;wherein the bottom face of said first non-woven fabric and the top faceof said third non-woven fabric are bonded by water adhesion, and saidsecond non-woven fabric and said first non-woven fabric are compressedvia a mold compressor to form the sheet product.
 3. A sheet shaped heatgenerating body comprising a plurality of non-woven fabrics mutuallysuperposed via water adhesion or water adhesion plus compression,wherein at least one of said non-woven fabrics holds a heat generatingcomposition inside its pores.
 4. A sheet shaped heat generating bodyaccording to claim 1 or 2, wherein said first non-woven fabric has asits main component fibers selected from pulp, cotton, linen and rayon,and wherein said first non-woven fabric has a porosity rate of 60-99.5%,is 0.5-25 mm thick, and weighs 5-200 g/m².
 5. A sheet shaped heatgenerating body according to claim 1, wherein said second non-wovenfabric has as its main component fibers selected from pulp, cotton,linen and rayon, and wherein said second non-woven fabric weighs 5-150g/m².
 6. A sheet shaped heat generating body according to any one ofclaims 2 through 5, wherein said heat generating powder composition hasas its main components iron powder and activated carbon, or iron powder,activated carbon and inorganic electrolytes, etc. and includes a solidcomponent which contacts with the oxygen in air to generate heat.
 7. Asheet shaped heat generating body according to any one of claims 1 and2, wherein said first and second non-woven fabrics are superposed byadhering water on the top face of said first non-woven fabric and/or abottom face of said second non-woven fabric.
 8. A sheet shaped heatgenerating body according to claim 5, wherein the amount of wateradhered to said bottom face of said first non-woven fabric is 10-200g/m².
 9. A sheet shaped heat generating body according to any one ofclaims 1 through 3, wherein said non-woven fabrics include a joggle faceformed from an embossed face of said mold compressor.
 10. A method ofmanufacturing a sheet shaped heat generating body, comprising the stepsof:adhering water to a bottom face of a porous, first non-woven fabric;spraying a heat generating powder composition on a top face of saidfirst non-woven fabric, wherein said heat generation powder compositionis held inside pores of said first non-woven fabric; superposing asecond non-woven fabric on said top face of said first non-woven fabricand subsequently compressing said first non-woven fabric and said secondnon-woven fabric via a mold compressor to form a sheet product; andimpregnating said sheet product with water or a solution of inorganicelectrolytes in water.
 11. A method of manufacturing a sheet shaped heatgenerating body, comprising the steps of:adhering water to a bottom faceof a porous, first non-woven fabric and/or a top face of a thirdnon-woven fabric; superposing said third non-woven fabric on said bottomface of said first non-woven fabric; spraying a heat generating powdercomposition on a top face of said first non-woven fabric, wherein saidheat generating powder is held inside pores of said first non-wovenfabric; superposing a second non-woven fabric on said top face of saidfirst non-woven fabric and subsequently compressing said first non-wovenfabric and said second non-woven fabric via a mold compressor to form asheet product; and impregnating said sheet product with water or asolution of inorganic electrolytes in water.
 12. A method ofmanufacturing a sheet shaped heat generating body, comprising the stepsof:superposing a plurality of layers of a first non-woven fabric and asecond non-woven fabric or of a first non-woven fabric, a secondnon-woven fabric and a third non-woven fabric via water adhesion orwater adhesion plus compression, and causing a heat generating powder tobe held in pores of at least one of said non-woven fabrics.
 13. A methodof manufacturing a sheet shaped heat generating body according to anyone of claims 10 through 12, wherein said first non-woven fabric has asits main component fibers chosen from pulp, cotton, linen and rayon, andwherein said first non-woven fabric has a porosity rate of 60-99.5%, is0.5-25 mm thick, and weighs 5-200 g/m².
 14. A method of manufacturing asheet shaped heat generating body according to claim 10, wherein saidsecond non-woven fabric has as its main component fibers selected frompulp, cotton, linen and rayon, and wherein said second non-woven fabricweighs 5-150 g/m².
 15. A method of manufacturing a sheet shaped heatgenerating body according to any one of claims 10 through 12, whereinsaid heat generating powder composition has as its main component ironpowder and activated carbon, or iron powder, activated carbon andinorganic electrolytes, and includes a solid component which generatesheat when said solid component comes into contact with oxygen in air.16. A method of manufacturing a sheet shaped heat generating bodyaccording to any one of claims 10 through 12, wherein said first andsecond non-woven fabrics are superposed by adhering water to said topface of said first non-woven fabric and/or a bottom face of said secondnon-woven fabric.
 17. A method of manufacturing a sheet shaped heatgenerating body according to claim 16, wherein the amount of wateradhered to said bottom face of said first non-woven fabric and/or saidtop face of said second non-woven fabric is 10-200 g/m².
 18. A method ofmanufacturing a sheet shaped heat generating body according to any oneof claims 10 through 12, wherein said mold compressor has embossing onat least one of its compressing faces.
 19. A sheet shaped heatgenerating body according to claim 2, wherein at least one of saidsecond and third non-woven fabrics has as its main component fibersselected from pulp, cotton, linen and rayon, and wherein said secondnon-woven fabric weighs 5-150 g/m².
 20. A method of manufacturing asheet shaped heat generating body according to any one of claims 11 and12, wherein at least one of said second and third non-woven fabrics hasas its main component fibers selected from pulp, cotton, linen andrayon, and wherein said second non-woven fabric weighs 5-150 g/m².